The magnetic compass is the workhorse of navigation instruments because it provides three things:

• Real time compass headings whether your boat is dead in the water, on a plane or moving slowly against an outgoing tide, the compass gives the boat heading. 
• Straight line steering helps the helmsman avoid steering a serpentine path when steering by the compass heading. 
• Reliability in all situations is a given and it works without power.

That is why every boat needs a compass.